1. Field of the Invention
The present invention relates to a method of and an apparatus for controlling a data storage system, and a medium, and more particularly, to a method of and an apparatus for controlling a data storage system according to a temperature at which a write head pole tip thermally expands, by supplying the writing head with a predetermined warming current in a low temperature environment, so as to prevent degradation of writing characteristics of a signal on a disk in an initial writing stage, and a medium.
2. Description of the Related Art
A hard disk drive writes data received from a host computer or reads data written on a hard disk using a magnetic head. Nowadays, since hard disks are manufactured to have a large capacity and a small size, the number of bits that can be fit on each track, i.e., BPI (bit per inch), and the number of tracks that can be fit on the disk, i.e., TPI (tracks per inch), increase, and therefore, more sophisticated and rapid method and mechanism for controlling a head position are needed.
Typically, at a low temperature, the hard disk drive shrinks, and a coercive force increases due to its magnetic physical characteristics. As a result, it becomes difficult to write the data on a medium in comparison with a normal or high temperature case.
Further, a pole tip of a writing head thermally expands due to a high temperature inside the hard disk drive. Because of this, in an initial writing stage, the pole tip shrinks at the low temperature and then thermally expands at the high temperature due to a writing current. The pole tip thermally expands until it reaches a saturation state when the writing current is continuously applied to the pole tip for a predetermined time.
The pole tip shrinks at the low temperature as shown in FIG. 1A. If the writing current starts flowing through the writing head by a writing command, the pole tip keeps expanding during the initial writing stage as shown in FIG. 1B. Then, after a temperature of the pole tip has been sufficiently raised due to the writing current applied for the predetermined time, the pole tip thermally expands until the saturation state as shown in FIG. 1C.
Due to the foregoing, a flying height of the writing head from a disk surface of the medium becomes changed. Therefore, the flying height in the initial writing stage increases temporarily until the pole tip thermally expands, and so a level of a signal written in an initial writing sector is reduced when the signal is reproduced. Because of this, repeated errors appear when the data written in a sector of the initial writing sector is reproduced. Especially, at the low temperature, reading errors occur more frequently in the initial writing sector.
To solve the above problem, a conventional dummy write method has been introduced. As shown in FIG. 2, the pole tip of the writing head expands by performing dummy write method in a gap between sectors before the writing head reaches a target sector (for example, a sector 100). However, in the dummy write method performed in the hard disk drive, a number of bytes which are dummy written are changed according to a head position of the writing head with respect the disk surface of the medium. The average number of bytes which are dummy written is about 1.5 track * a number of data sectors * 6 bytes. Then, when the number of bytes which are dummy written is small, according to the head position, initial writing characteristics of the writing head degrade.
Even if the number of bytes which are dummy written is sufficiently large, and then the above problem may be solved, a delay in a writing time still occurs.